Device for indicating the presence of a train



Feb. 28, 1967 H. J. M. DELUGEAU 3,307,032

- DEVICE FOR INDICATING THE PRESENCE OF A TRAIN Filed Oct. 1, 1963 2 Sheets-Sheet l INVENTOR.

HENRI J M. DELUGEAU AG ENT Feb. 28, 1957 H. J. M. DELUGEAU 33@7,@32

DEVICE FOR INDICATING THE PRESENCE OF A TRAIN 2 Sheets-Sheet 2 Filed Oct.

N S N N E ld 2F M C P Um C S C v E U B M m B E m w a J B y R A m 1W A I m my SC RSN INVENTOR. HENRI J. M. DELUGEAU United States Patent 3,307,032 DEVICE FOR INDICATING THE PRESENCE OF A TRAIN Henri Joseph Marie Delugeau, Montrouge, Seine, France, assignor to North American Philips Company, Inc., New York, N.Y., a corporation of Delaware Filed Oct. 1, 1963, Ser. No. 312,940 Claims priority, application France, Oct. 3, 1962, 911,144 Claims. (Cl. 24634) The invention relates to a device for indicating the presence of a train in a given part of a railway track.

Devices for indicating the presence of a train in a railway track are already known, in which the rails of the railway track are insulated with respect to each other and to those of adjacent tracks and are connected to a signal source, while in addition an indication device is available which is controlled by the signal voltage between the rails. If no train is present in the track in question, the indication device consequently receives, through the rails, a signal voltage by which, under the control of the indication device, an indication relay is energized. However, if a train is in the track, the rails are shortcircuited through the wheels and shafts of the train so that the signal voltage disappears and the indication relay becomes de-energized. In general, the signal-source and the indication device are provided on opposite ends of the railroad track because, if the train is between the signal source and the indication device, it causes an effective short-circuit which would not always be guaranteed if, for example, the signal source and the indication device were provided at the same end of the track and the train would be in the track at some distance therefrom because the rails may have a certain impedance.

In known devices, the presence of a train is signalled independent of the position of the train in the section. In certain circumstances, this may be disadvantageous, for example, if in a comparatively long railroad section an automatically operated level crossing occurs. In principle, the crossing need be closed only when the train has approached to within a comparatively short distance, while the crossing can be opened again immediately after the train has passed. If the control of the crossing is made to be dependent upon the said section indication device, the crossing would consequently be closed as soon as the train enters the section and would be opened only after the train has left the section. In this case, unnecessarily long waiting times would occur for the public.

There consequently exists a need for a device which indicates the presence of a train only if the train is in a given part of the railroad section.

Various solutions of this problem are already known which, however, are comparatively expensive and complicated.

One solution in which the level crossing is closed a predetermined period of time after the train has entered the section is not entirely satisfactory in practice.

In another solution, a part of the rail circuit which shows a certain inductance is included in the tuned circuit of a high-frequency oscillator. When a train approaches, the conditions of the oscillator are consequently varied. However, this solution can be used only over comparatively short distances, while in addition, the distance to the train is not accurately determined.

A device in which the desired determined part of a section is insulated from the rest of the section and in which a separate signal source and signal receiver is used, is very expensive, in particular in view of the price of the rail insulation which, in general, requires very heavy choke coils for passing the traction current.

The invention provides a simple and cheap solution to the problem.

According to the invention, in a railway section of which the rails are insulated with respect to each other and to those of adjacent sections and are connected to a signal source and to an indication device which is controlled by the signal voltage between the rails, an auxiliary indication device is provided between the signal source and the said first indication device, said auxiliary indication device preferably being coupled inductively to the rails and controlled by the signal current flowing across the rails.

In order that the invention may readily be carried into effect, it will now be described more fully, by way of example, with reference to the accompanying drawings, in which:

FIGS. 1, 2 and 3 show various embodiments of the invention for supplying an indication when a train drives between two given points of the section,

FIG. 4 shows an example of a known overlap system, and

FIG. 5 shows the use of the invention in such a system.

Referring now to FIG. 1, 8V]. is a railroad section the ends of which are insulated from the adjacent sections by insulating joints J11, J21, I31 and J41. At the righthand end, the signal transmitting source EV1 is connected between the rails and on the left-hand end, the signal receiver RV1 is connected between the rails and controls a section relay ReVl which normally is energized under the influence of the signals received through the rail circuit from the source EV1. This device is known per se. As was already noted, the relay ReVl becomes de-energized if a train is present in the section SVl because the rails are shortcircuited by the train and the receiver RV1 consequently receives no signal.

Let it now be assumed that the section SVI is comparatively long and that there is an automatically operated level crossing PN at the right-hand end. In this case, it is desirable in order to prevent the closing of the crossing for an excessively long period of time, to have the disposal of a device which responds only if a train which normally moves in the direction of the arrow SC, is in the section AB of the track SVI, the point A being located at a suitable distance before the crossing. T herefore, according to the invention, a signal receiver RS1 is provided at the point A at the beginning of the track segment AB. The receiver is coupled inductively to the rail circuit through the coils C11 and C12 in known manner by means of a magnetic core and controls an indication relay ReSl. In the rest condition, if no train is present in the section SVI, a signal current flows across the loop formed by the rails and the signal receiver RV1. In response to this current, a signal voltage is induced, through the coils C11 and C12, in the receiver RS1 and the relay ReSl is energized. Now, if a train enters the section SVl from the left, the receiver RV1 is shortcircuited, it is true, and the relay ReVl becomes de-energized. However, the loop formed by the rails remains shortcircuited through the wheels and shafts of the train so that a signal current continues to flow'through the rails and the receiver RS1 until the train has reached the point A. If parts of the train are between the points A and B, the rails are shortcircuited between the receiver RS1 and the signal source EV1. Then the signal current flows back to the source EV1 through this shortcircuit and the receiver RS1 no longer receives a signal. As a result, the relay ReSl becomes de-energized under the control whereof the crossing PN is closed. Also, if the train is on the right-hand side of the signal source EV1, the receiver RS1 receives no signal because the source EV1 remains shortcircuited until the train has left the 3 section SVl. Then the relays ReVl and ReSl are again energized and the crossing is opened.

In principle, the receiver RS1 could be coupled to one of the rails only. However, it is advantageous to couple the receiver to both rails because interference currents which have the same direction in both rails are then neutralized.

FIG. 2 shows the case in which the track segment AB, in which the presence of a train is to be signalled, for example, because a level crossing is present in the proximity of the point B, overlaps part of two adjacent sections SV21 and SV22. In this case, the signal sources EV21 and EV22 associated with the sections are provided in the proximity of the rail insulations J 12 and J22, while the receivers RS21 and R822 are provided at the beginning and the end of the desired track AB. Analogous to the device shown in FIG. 1, the relay ReS21 controlled by the receiver RS21 will be energized until the rails between the receiver RS21 and the rail insulations J 12 and J22 are shortcircuited by parts of a train. The relay R0822, controlled by the receiver RS22 will .be energized as long as no train is present between the rail insulations J12 and I22 and the receiver RS22. So, if a train is present somewhere in the track AB, at least one of the relays ReS21 and ReS22 will be in the rest condition.

Accordingly, voltages rReS21 and rReS22 are supplied by the relays in known manner to the or gate P2 if the relays are in the rest condition so that an output voltage CS is obtained if a train is present in track AB.

In the case of FIG. 3, the track segment AB, in which the presence of the train is to be signalled, is located somewhere in the railroad track section 8V3 which is at some distance from the insulated ends thereof. In this case, signal sources EV31 and EV32 are provided at the left-hand and right-hand ends of the section SV3 and supply different signals, for example, signals of different frequencies. The signal source EV32 co-operates in known manner with the receiver RV3 on the left-hand end connected between the rails. In addition, at the beginning and the end of the track AB, the receivers RS3] and R832 are coupled inductively to the rails. The former receiver is sensitive only to the signals of the source EV32 and the latter to the signals of the source EV31. As may be clear from the above, the relay ReS31 controlled by the receiver R831 is energized unless a train is present in the section SV3 on the right of the point A and the relay controlled by the receiver RS32 will be energized unless a train is present on the left of the point B. Only if a train is present in the track AB will the two relays ReS31 and ReS32 be in the rest condition. For indication, the relays in the rest condition convey voltages rReS31 'and rReS32 to the inputs of the and circuit P3 so that the latter will supply an output voltage CS if a train is present in the track AB.

FIG. 4 diagrammatically shows an example of a known so-called overlap system. In this case, the rails are indicated by a single line for simplicity. Along the track V, signals SA, SB, SC SN are provided near the section boundaries A, B, C N where the rails are insulated with respect, to those of adjacent sections by means of insulating joints JA, JB, JC JN.

Generally speaking, the input signal of a section in which a train is driving is set red, the input signal of the preceding section yellow and the input signal of further preceding sections green. In overlap signalling, however, the input signal of the preceding section is first set yellow and the input signals of further preceding sections green when the train has already covered a certain security distance d in the section in question. In order to be able to signal this, for example, in known overlap systems, at a distance d behind the beginning A, B etc. of each section, auxiliary rail insulations JA', JB' etc. are provided and the thus obtained subsections are each provided with a signal receiver RA, RA, RB, RB etc.

4- and signal sources EA, EA, EB, EB etc., as is shown in FIG. 4.

For example, if a train enters the section BC from the left, which is indicated through the receiver RB, the signal SB will immediately set red, while the signal SA of the preceding section, which was set red, is set yellow only if the train has covered the distance d in the section BC, which is indicated through the receiver RB.

Also, the signal SC will be set red as soon as the train has passed the point C (indicated by the receiver RC) while the signal SB is set yellow and the signal SA green when the train has covered the distance d indicated by the receiver RC, etc. This system requires a number of additional rail insulations and signal sources and consequently is rather expensive.

FIG. 5 shows how, in accordance with the invention, such an overlap system can be simplified by reducing the number of required signal sources and rail insulations to half its original number. In the embodiment, at the inputs A, B, C etc. of the sections where the signals SA, SB, SC etc. are provided, receivers RSA, RSB, RSC are provided which are coupled inductively to the rails. At a safety distance a from the beginning of each section, the rails are insulated by insulating joints Ia, 1b, 10 and so on. On the left-hand side of these joints signal sources EA, EB, EC and so on are connected between the rails and on the right-hand side thereof receivers RB, RC and so on.

The various receivers again control further indicating relays which are not shown.

The presence of a train in a distance d after the input A, B or C etc. of the sections is signalled by the receivers RSA, RSB etc. and the presence of a train in the tracks between the insulated rail joints by the receivers RB, RC etc.

FIG. 5 further cliagramatically shows how, for example, the signal SA can be controlled. As may be clear from the above, the signal SA must be set red when a train is present between the starting point A of the section and the point Jb, which means that at least one of the receivers RSA or RB receives no signal. The signalling condition red (R) is controlled accordingly through the or gate PR, to which voltages rRSA and rRB are supplied if the receiver RSA or RB receives no signal.

The signal SA must assume the signalling condition yellow (I) if the whole train has passed the point Jb, which means that the receiver RC may not receive a signal, but the receivers RSA and RB do receive signals. The signalling condition yellow (1) is controlled accordingly by the and gate P], to which voltages tRSA and tRB are supplied by means of the receivers RSA and RB if they receive signals, to which a voltage rRC is supplied by the receiver RC if it receives no signal.

Finally, the signal SA must be set green (V) if the whole train has passed the point Jc, which means that the receivers RSA, RB and RC all must receive signals. Under these circumstances, the receivers supply voltages tRSA, tRB and IRC to the and gate PV, the output voltage of which controls the signalling condition green (V). Although FIG. 5 shows the signal devices SA, SB, etc. and the various signal receivers and signal sources located in consecutive track sections, it will be obvious that one or more sections may be skipped so long as the general sequence illustrated is maintained.

What is claimed is:

1. In a track circuit of the type which is divided into a plurality of insulated sections, a system for detecting the presence of a train within a given segment of the track circuit for one given direction of train travel, said given segment being located within a given one of said insulated sections of the track circuit, comprising first and second signal transmitting means coupled to said given section of track circuit at first and second points, respectively, outside of said given segment and on opposite sides thereof, said first and second transmitting means supplying to said track circuit first and second signals, respectively, having different characteristics, first and second signal detecting means coupled to the track circuit at the end points of said given segment, each of said first and second signal detecting means being responsive only to the signals supplied to the track circuit by the corresponding signal transmitting means located at the other side of the other one of said first and second detecting means, each of said signal detecting means receiving the respective signal it is responsive to only if the portion of the track circuit between itself and its corresponding signal transmitting means is unoccupied by a train, train indicating means located along said track circuit, and means for supplying signals from said first and second detecting means to said train indicating means so as to actuate said indicating means only when respective track signals to both of said detecting means are simultaneously interrupted.

2. A system as described in claim 1 wherein said first and second transmitting means supply first and second signals, respectively, of different frequencies to the track circuit and said first and second detecting means each comprise frequency selective means responsive to a given one of said diiferent frequency signals.

3. A system as described in claim 1 wherein said signal supplying means do not include said track circuit.

4. A system as described in claim 1 wherein said signal supplying means further comprises gating means serially connected between the outputs of said first and second detecting means and the input of said indicating means and arranged to provide an AND function.

5. A system as described in claim 1 wherein said first and second detecting means are inductively coupled to the track circuit and wherein said first and second transmitting means are respectively located in the vicinity of the insulating rail joints at either end of said given section of track circuit.

6. A train signalling system for a stretch of railroad track divided into a plurality of sections insulated from one another by spaced insulating rail joints, comprising a plurality of signalling devices each of which is located in 'a difierent track section at a predetermined distance from corresponding ones ofsaid rail joints, a plurality of first and second signal detecting devices coupled to the track circuit, a plurality of signal transmitting means coupled to the track circuit to supply track signals thereto, each of given ones of said sections comprising a first signal detecting device located near one rail joint of the section, a second signal detecting device located near the signalling device of the section, and a signal transmitting means loacted near the rail joint at the other end of the section, said first and second detecting devices being responsive to the track signal supplied by the correspond ing signal transmitting means to selectively provide at their outputs given signals determined by the reception or interruption of the track signal thereat, and means for coupling the output of the second signal detecting device of a first one of said sections, the output of the first signal detecting device of a second one of said sections, and the output of the first signal detecting device of a third one of said sections to the signalling device of said first section so as to turn said signalling device red upon the interruption of the track signal to said first section second detecting device or to said second section first detecting device, and to turn said first section signalling device yellow upon the simultaneous receipt of the track signals by said first section second detecting device and said second section first detecting device and the interruption of the track signal to said third section first detecting device, and to turn said first section signalling device green upon the simultaneous receipt of the track signals by said first section second detecting device, said second section first detecting device and said third section first detecting device.

7. A system as described in claim 6 wherein said first and second signal detecting devices and said signal transmitting means of each of said given ones of said sections is arranged in the following order in the direction of train travel: said first signal detecting device, said second signal detecting device, and said signal transmitting means.

8. A system as described in claim 7 wherein each one of said plurality of first signal detecting devices is connected between the rails of the track circuit and each one of said second signal detecting devices is inductively coupled to said rails.

9. A system as described in claim 7 wherein said coupling means further comprises OR gating means having first and second inputs to which said first section second detecting device and said second section first detecting device are coupled, respectively, first AND gating means having first, second and third inputs to which said first section second detecting device, said second section first detecting device and said third section first detecting device are coupled, respectively, and second AND gating means having first, second and third inputs to which said first section second detecting device, said second section first detecting device and said third section first detecting device are coupled, respectively.

10. A system as described in claim 6 wherein said first, second and third track sections are sequentially arranged in that order as viewed from the direction of train travel.

References Cited by the Examiner UNITED STATES PATENTS 2,224,395 12/1940 Kemmerer 246-249 X 2,719,218 9/1955 Miller 246-430 3,046,392 7/1962 Luft 246- FOREIGN PATENTS 80,620 4/ 1963 France.

ARTHUR L. LA POINT, Primary Examiner. S. B. GREEN, Assistant Examiner. 

1. IN A TRACK CIRCUIT OF THE TYPE WHICH IS DIVIDED INTO A PLURALITY OF INSULATED SECTIONS, A SYSTEM FOR DETECTING THE PRESENCE OF A TRAIN WITHIN A GIVEN SEGMENT OF THE TRACK CIRCUIT FOR ONE GIVEN DIRECTION OF TRAIN TRAVEL, SAID GIVEN SEGMENT BEING LOCATED WITHIN A GIVEN ONE OF SAID INSULATED SECTIONS OF THE TRACK CIRCUIT, COMPRISING FIRST AND SECOND SIGNAL TRANSMITTING MEANS COUPLED TO SAID GIVEN SECTION OF TRACK CIRCUIT AT FIRST AND SECOND POINTS, RESPECTIVELY, OUTSIDE OF SAID GIVEN SEGMENT AND ON OPPOSITE SIDES THEREOF, SAID FIRST AND SECOND TRANSMITTING MEANS SUPPLYING TO SAID TRACK CIRCUIT FIRST AND SECOND SIGNALS, RESPECTIVELY, HAVING DIFFERENT CHARACTERISTICS, FIRST AND SECOND SIGNAL DETECTING MEANS COUPLED TO THE TRACK CIRCUIT AT THE END POINTS OF SAID GIVEN SEGMENT, EACH OF SAID FIRST AND SECOND SIGNAL DETECTING MEANS BEING RESPONSIVE ONLY TO THE SIGNAL SUPPLIED TO THE TRACK CIRCUIT BY THE CORRESPONDING SIGNAL TRANSMITTING MEANS LOCATED AT THE OTHER SIDE OF THE OTHER ONE OF SAID FIRST AND SECOND DETECTING MEANS, EACH OF SAID SIGNAL DETECTING MEANS RECEIVING THE RESPECTIVE SIGNAL IT IS RESPONSIVE TO ONLY IF THE PORTION OF THE TRACK CIRCUIT BETWEEN ITSELF AND ITS CORRESPONDING SIGNAL TRANSMITTING MEANS IS UNOCCUPIED BY A TRAIN, TRAIN INDICATING MEANS LOCATED ALONG SAID TRACK CIRCUIT, AND MEANS FOR SUPPLYING SIGNALS FROM SAID FIRST AND SECOND DETECTING MEANS TO SAID TRAIN INDICATING MEANS SO AS TO ACTUATE SAID INDICATING MEANS ONLY WHEN RESPECTIVE TRACK SIGNALS TO BOTH OF SAID DETECTING MEANS ARE SIMULTANEOUSLY INTERRUPTED. 